APOD: Cassini's Last Ring Portrait at Saturn (2017 Sep 26)

[APOD Robot]

Cassini's Last Ring Portrait at Saturn

Explanation: How should Cassini say farewell to Saturn? Three days before plunging into Saturn's sunny side, the robotic Cassini spacecraft swooped far behind Saturn's night side with cameras blazing. Thirty-six of these images have been merged -- by an alert and adept citizen scientist -- into a last full-ring portrait of Cassini's home planet for the past 13 years. The Sun is just above the frame, causing Saturn to cast a dark shadow onto its enormous rings. This shadow position cannot be imaged from Earth and will not be visible again until another Earth-launched spaceship visits the ringed giant. Data and images from Cassini's mission-ending dive into Saturn's atmosphere on September 15 continue to be analyzed.

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[Ann]

Note the tinge of blue in parts of Saturn's limb.

Ann

[Boomer12k]

Outstanding view...
It amazes me that while traveling through the rings, they were so thin, and you could not make out any ice chunks, I guess none were near enough... also you can see the outermost ring at the sides...but not front side or back....unless you click on the image and then zoom in...

:---[===] *

[De58te]

Interesting anomaly about the shadow. Note you can see it better if you zoom in the large version of the photo and bring the viewing screen brightness or contrast control up to about 80% because it is a fine detail. Saturn's shadow is slightly darker than the night side of its atmosphere I presume because some light reflects back from the rings and satellites. Sort of like a total lunar eclipse. Now the shadow arcs downwards from Saturn because Saturn itself is round. Yet on the far left edge of the shadow and the night side of Saturn there is a distinct arc raised up above the shadow curve. It is as if an object almost the size of Earth was just beyond Saturn's left rim. (Size estimated from Saturn's diameter being about 9 times larger than Earth.) Yet I don't see any bulge in the sunlit rim of Saturn. What could cause this? Is it just a glitch in the camera?

[orin stepanek]

Makes a nice PC Wallpaper

[Case]

Interesting anomaly about the shadow. […] Yet on the far left edge of the shadow and the night side of Saturn there is a distinct arc raised up above the shadow curve.

I presume that is an image edit/cleanup that was supposed to stay hidden in the shadows. There is a another such broad brush stroke, a bit up from the same spot as the other, just above the rings.

[heehaw]

Adios, Saturn!

[heehaw]

Outstanding view...
It amazes me that while traveling through the rings, they were so thin, and you could not make out any ice chunks, I guess none were near enough... also you can see the outermost ring at the sides...but not front side or back....unless you click on the image and then zoom in...
:---[===] *

I am still more than annoyed that they did not 'end' the mission by having Cassini gently join a ring. We would have received wonderful close-ups of snowballs on parade! The pollution argument is silly - Saturn itself may well have been polluted by the chosen demise.

[Chris Peterson]

Outstanding view...
It amazes me that while traveling through the rings, they were so thin, and you could not make out any ice chunks, I guess none were near enough... also you can see the outermost ring at the sides...but not front side or back....unless you click on the image and then zoom in...
:---[===] *

I am still more than annoyed that they did not 'end' the mission by having Cassini gently join a ring. We would have received wonderful close-ups of snowballs on parade! The pollution argument is silly - Saturn itself may well have been polluted by the chosen demise.

Saturn cannot be polluted by Cassini because there's nothing in Cassini that isn't already found in Saturn in vastly higher amounts (and the dynamics of the atmosphere will distribute that material over a huge volume). There was enough material in Cassini, however, to seriously alter the surfaces of any of the moons, potentially damaging our abilities to conduct future science.

They made the right decision.

[boonedickmann@gmail.com]

Over 13 years ago I downloaded "finalsaturn" and I have always considered it the finest portrait ever taken. Now I have a companion!

[Catalina]

I, too, noticed the dark semi-circular shaped "brushstroke" on the far left of the shadow on the planet and I think there is also a smaller one on the far right. Does anyone else see a fine red line on the edges of the elements on the left side of the image and fine green lines on the edges of the elements on the right side? I saw the same light refractions on some of the photos I took of the Great American Eclipse in August. As an amateur, I don't know if this is a common phenomenon in photography of lighted celestial objects?

[Amateur Craig]

Is the color normal or enhanced???
Either way, this is certainly an awesome photo compilation..

[Ann]

Note the tinge of blue in parts of Saturn's limb.

Ann

I take back what I said about the color of Saturn's limb. I looked at the APOD at work, and my computer there made it look blue. My home computer doesn't. In fact the colors don't overlap, and Saturn's left limb is red, with a blue arc just inside it. The right side of the limb is green.

My eye just spotted the blue arc inside the red one, and I thought that the whole thing was blue. How typical of me.

The left side of the F-ring shows the same red-blue separation as Saturn's left limb. Even so, the F-ring looks slightly bluer than the other rings to me.

Ann

[Ann]

Interesting anomaly about the shadow. […] Yet on the far left edge of the shadow and the night side of Saturn there is a distinct arc raised up above the shadow curve.

I presume that is an image edit/cleanup that was supposed to stay hidden in the shadows. There is a another such broad brush stroke, a bit up from the same spot as the other, just above the rings.

Thanks, Case!

Ann

[rstevenson]

Note the tinge of blue in parts of Saturn's limb.

I take back what I said about the color of Saturn's limb. I looked at the APOD at work, and my computer there made it look blue. My home computer doesn't. In fact the colors don't overlap, and Saturn's left limb is red, with a blue arc just inside it. The right side of the limb is green.

My eye just spotted the blue arc inside the red one, and I thought that the whole thing was blue. How typical of me.

The left side of the F-ring shows the same red-blue separation as Saturn's left limb. Even so, the F-ring looks slightly bluer than the other rings to me.

For reference, here's a screen grab showing my Digital Color Meter hovering over the area down near the bottom-left visible edge of the lit area of Saturn. (My cursor was 'grabbed', but was almost directly to the left of the bottom edge of the enlarged area inside the meter's window.) On my screen that reddish area is a bright violet, and the blueish area is a range of teal tones.

Rob

[Ann]

Note the tinge of blue in parts of Saturn's limb.

I take back what I said about the color of Saturn's limb. I looked at the APOD at work, and my computer there made it look blue. My home computer doesn't. In fact the colors don't overlap, and Saturn's left limb is red, with a blue arc just inside it. The right side of the limb is green.

My eye just spotted the blue arc inside the red one, and I thought that the whole thing was blue. How typical of me.

The left side of the F-ring shows the same red-blue separation as Saturn's left limb. Even so, the F-ring looks slightly bluer than the other rings to me.

For reference, here's a screen grab showing my Digital Color Meter hovering over the area down near the bottom-left visible edge of the lit area of Saturn. (My cursor was 'grabbed', but was almost directly to the left of the bottom edge of the enlarged area inside the meter's window.) On my screen that reddish area is a bright violet, and the blueish area is a range of teal tones.

colour fringe.jpg
Rob

Thanks! Interesting!

Ann

[rstevenson]

I mis-spoke myself, to quote a famous US President. I meant to say "my cursor was not 'grabbed'", of course. I'd edit my post, but then it wouldn't agree with your quote of it, Ann. Oh well.

Rob

[Chris Peterson]

I take back what I said about the color of Saturn's limb. I looked at the APOD at work, and my computer there made it look blue. My home computer doesn't. In fact the colors don't overlap, and Saturn's left limb is red, with a blue arc just inside it. The right side of the limb is green.

Presumably this is a consequence of the fact that color images from the Cassini imaging system are made by taking separate exposures through different filters, and there is some movement of the spacecraft with respect to the target between those exposures.

[geckzilla]

I take back what I said about the color of Saturn's limb. I looked at the APOD at work, and my computer there made it look blue. My home computer doesn't. In fact the colors don't overlap, and Saturn's left limb is red, with a blue arc just inside it. The right side of the limb is green.

Presumably this is a consequence of the fact that color images from the Cassini imaging system are made by taking separate exposures through different filters, and there is some movement of the spacecraft with respect to the target between those exposures.

No presumption necessary; this is the exact reason. Though it is also important to note that there are various ways to process the image to minimize these outcomes, so if we see another version of the same dataset, it's totally possible for it to be even better (or worse!) in that regard.

[neufer]

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